Method and apparatus for determining water content in gaseous media



Aprll 5, 1966 J, ss ETAL 3,244,602

METHOD AND APPARATUS FOR DETERMINING WATER CONTENT IN GASEOUS MEDIAFiled Oct. 2, 1961 4 Sheets-Sheet 1 NE z E n O M Q 0: 2& 5 0 N n: Q- D ZI) Q Q INVENTORS.

JOHN R. GLASS a EDWARD J. MOORE BY @LQ/ ATTORNEYS SAMPLE SOURCE April 5,1966 J. R. GLASS ETAL 3,244,602 METHOD AND APPARATUS FOR DETERMININGWATER CONTENT IN GASEOUS MEDIA 4 Sheets-Sheet 2 Filed Dot. 2, 1961 allmOmDOm EOPOE ll mwomoomm nimm ws vs INVENTORS. JOHN R. GLASS 8\ EDWARDJ. MOORE flew $7 M ATTORNEYS Aprll 5, 1966 .1. R. GLASS ETAL 3,244,602

METHOD AND APPARATUS FOR DETERMINING WATER CONTENT IN GASEOUS MEDIAFiled Oct. 2, 1961 4 Sheets-Sheet 5 TIME MINUTES 0 IO 20 30 4 0 50 so IVALVES I5, 22 OPEN VALVES 3|, 31, 43 OPEN I so so Fla 3/! ELECTROLYSISCURRENT I FLOWING I 410 6'0 RECORDER CHART I DRIVE RUNNING |43,4s-

RECORDER METER i Q INDICATING I 33,45}

TIME OF EVENT, MINUTES IO 20 310 40 5O 6O SWITCH PATTERNS I INVENTORS.

JOHN R. GLASS a F/G 35 BY EDWARD J. MOORE their ATTOR/VE Y5 April 5,1966 J. R. GLASS ETAL METHOD AND APPARATUS FOR DETERMINING WATER?CONTENT IN GASEOUS MEDIA Filed Oct. 2, 1961 4 Sheets-Sheet 4.

ms POINT ON LEFT END OF RECORD (.27rno) INDICATES I WATER CONTENT x2 54:00 5 5=oo LL] 5 E e=oo l" l- 2 7 00 hi a: 8-00 8 .4 Lo

/ CURRENT, MILLIAMPERES WATER, PFM -O 0 IO 20 3O 4O 5O 6O 7O 8O 90 I00IIO I20 I30 INVENTORS.

JOHN R. GLASS a EDWARD J. MOORE ATTORNEYS United States Patent 0 ice3,244,602 MEIHGD AND APPARATUS FDR DETERMHNINS WATER CONTENT IN GASEGUSMEDIA John R. Glass, Glasshoro, and Edward J. Moore, Woodhury, NJ. FiledOct. 2, 1961, Ser. No. 142,098 2 Claims. (Cl. 204-4) This inventionrelates to a method and apparatus for determining the Water content of agaseous specimen and, more particularly, to a method and apparatus forsemicontinuously measuring small concentrations of water in a gaseousstream, although it is not limited to such use.

In many chemical and other processes, the water content in a gaseousstream has a significant effect upon the process and efforts have beenmade heretofore to devise apparatus for continuously determining thewater content in such streams so that appropriate corrective action maybe taken, if necessary. In one form of device that has been developedfor this purpose, the gaseous stream is passed through a specialelectrolytic cell in which all entering water is continuously andquantitatively absorbed and electrolyzed to hydrogen and oxygen. Sincethe quantity of electricity required to electrolyze water is known, thewater content of the stream is determined by measuring the electrolysiscurrent.

While apparatus of this general character is effective for somepurposes, it has been found that the readings which it gives withcertain gaseous streams, notably those containing hydrogen, are notaccurate. The reason for this is believed to be that the oxygen releasedby the electrolysis tends to recombine with the hydrogen present in thestream to'form water which is again electrolyzed,

so that the water content readings obtained are high.

It is an object of the present invention, accordingly, to rovide animproved method and apparatus for measuring the water content of gaseousmedia which is free from the above-mentioned deficiencies of the priorart.

A further object of the invention is the provision of an electrolyticmethod and apparatus for semicontinuously determining the water contentof a gaseous specimen stream in which no opportunity is afforded for thegasdetermining cell alternately to absorb moisture from a gaseous sampleand to electrolyze moisture thus absorbed. in the case of a gaseoussample stream, the stream is caused to flow through the cell only duringthe moisture absorbing part of the operating cycle. During the part ofthe cycle devoted to electrolysis of the absorbed moisture, the samplestream is temporarily diverted from the cell so that there are no samplestream gas components present that might combine with the products ofthe electrolysis to form water. Preferably, an inert gas such asnitrogen is flowed through the cell during electrolysis to carry oh thehydrogen and oxygen thus produced. In this manner, it is possible toobtain highly accurate moisture-content determinations even with gaseoussamples containing a gas such as hydrogen that might combine with theproducts of the electrolysis to form Water. By alternately absorbingmoisture from a gaseous sample and electrolyzing it in this manner,determinations of Water content may be made semicontinuously.

' to control the'fiow through'the same.

3,244,5h2 Patented Apr. 5, 1966 Various other objects and advantageswill appear from the following detailed description of a typicalembodiment of the invention taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a simple flow diagram of a typical system according to theinvention for determining the water content of a gaseous sample stream;

FIG. 2 is a schematic diagram of a simplified electrical control circuitfor the water content determining system of FIG. 1;

FIGS. 3A and 3B are typical timing and switch pattern diagrams,respectively, for certain of-the operations carried out by the circuitof FIG. 2;

FIG. 4 is a typical water content record that might be produced byapparatus shown in'FIGS. l and 2; and

FIG. 5 is a representative calibration chart for a Water analyzer systemof the type shown in FIGS. 1 and 2.

Referring first to FIG. 1, a gaseous sample stream, which maycomprise,for example, gaseous hydrocarbon material in admixture withhydrogen from a petroleum refinery process stream, is supplied to theconduit'l'O of Water content determining apparatus embodying theinvention. From the conduit 16, the sample stream passes through a valve11, a conduit 12, a valve 13, aconduit 14, a solenoid operated valve 15,aconduit 16, a filter 17 and a conduit 18 to a water analysis cell19'for determining the water content of the gaseous stream suppliedthereto.

A pressure relief valve 24 may be connected to the conduit 12 betweenthe valves 11 and 13 to prevent the pressure in the system fromaccidentally'rising to 'an unsafe value. The filter 17 may be of anyknown type and it serves to prevent solid particles suspended in thegaseous sample from reaching the cell 19.

The cell 19 is preferably of the type disclosed in prior Patent No.2,830,945 to Keidel and further described in an article entitledDetermination of Water by Direct AmperometricMeasurement by F. A. Keidelwhich appears at page 2043 of Analytical Chemistry, volume 13, No. 12,December 1959. In a cell of this character, a hygroscopic electricallyconductive material absorbs moisture from any gas passing therethroughand'the cell can be energized electrically to electrolyze the moisturethus absorbed.

For proper operation of the water analysis cell 19, it is desirable thatthe sample flow therethrough be maintained at apredetermined arbitraryvalue. To this end, the output from the-cell 19 is fed through a conduit21, a solenoid operated valve 22 and a conduit 23 to conventional flowregulating apparatus which may'comprise, for example, a pressureresponsive flow regulator 24, a conduit 25, a conventional flowrestrictor device'26, and conduit 27 for sensing the pressure at theoutput of the flow restrictor device and supplying it to'the regulator24 The fiow regulator 24 functions automatically in the well knownmanner to maintain the pressure drop across the restrictor 26 at a valuesufficient to preserve a predetermined sample fiow rate through theWater analysis cell 19. The rate of flow can be measured in anyconventional manner as by a flow meter 28 connected by a-conduit 29 toreceive the output of the restrictor 26.

In order to maintain a constant rate of sample flow through the systemwhen the solenoid operated valves 15 and 22 are closed and the watersample collected by the water analysis cell 19 isbeing electrolyzed, aby-pass is provided which includes a conduit-30 connected to the conduit14, a solenoid operated valve '31, a' flow restricting orifice 32, and aconduit 33 connected to the conduit 23. The flow restricting orifice 32serves to restrict the sample flow through the by-pass so that thepressure of gas in the sample line will remain constant throughout theoperating cycle.

As will be described in greater detail hereinafter, after a water samplehas been collected by the water analysis cell 19 and the solenoidoperated valves 15 and 22 have been closed, it is desirable to flush outthe cell 19 with an inert gas and preferably to maintain the flow ofinert gas through the cell 19 while the water sample collected therebyis being electrolyzed. For this purpose, inert gas is supplied from asuitable source through a conduit 34, a conventional gas dryer 35, aconduit 36, a solenoid operated valve 37 and a conduit 38 which isconnected to the conduit 16. After passing through the cell 19, theinert gas is vented from the system over a path including a conduit 40connected to the conduit 21, a conventional flow restrictor device 41which may be a commercially available filter device or finely dividedinert material packed in a housing, a conduit 42 and a solenoid operatedvalve 43.

In accordance with the invention, a sample stream from the source ispassed through the cell 19 for a sutlicient period of time to permit anywater contained therein to be absorbed by the hygroscopic material inthe cell 19. The solenoid valves 15 and 22 are then closed, and thevalves 31, 37 and 43 are opened. The opening of the valve 31 permits thesample stream to flow through the by-pass described above, thusmaintaining the same rate of flow through the system, while the openingof the valves 37 and 43 permits inert gas to pass through the cell 19and to flush out all traces of the sample stream previously flowedtherethrough. Electric current is then passed through the cell 19 toelectrolyze the water sample absorbed by the hygroscopic materialtherein and the electrolysis current is measured and taken as anindication of the water content present in the sample stream.

While the steps outline briefiy above may be carried out by hand,automatic operation is preferred, a control system of the type shown inFIG. 2 being employed for this purpose. Referring to FIG. 2, the severaloperations may be controlled in sequence by a conventional timer 44driven by a synchronous motor 45 connected to the electrical power mains(not shown). The timer 44 may be of the type having a plurality of cams46, 47, 48, 49 and 50 on a common shaft which are adapted to actuate theswitches 51, 52, 53, 54 and 55, respectively, in predetermined sequenceas outlined in greater detail below.

The switch 51 has a movable contact arm 56 which normally engages afixed contact 57 and is adapted to be moved by the cam 46 intoengagement with a second contact 58. The movable contact arm 56 isconnected by a conductor 59 to one side of the power mains, the otherside being connected by a conductor 60 to the solenoid 22' and throughthe conductors 61, 62, 63 and 64 to one side of each of the solenoids43, 37', 31' and 15, for actuating the valves 22, 43, 37, 31 and 15,respectively. The other terminals of the solenoids 15' and 22 areconnected by the conductors 65 and 66 to the fixed switch contact 57,while the other terminals of the solenoids 31', 37' and 43' areconnected by the conductors 67, 68 and 69 to the fixed contact 58. Itwill be understood, therefore, that when the movable svdtch contact 56is in engagement with the fixed contact 57, the solenoids 15' and 22'will be energized and the valves 15 and 22 (FIG. 1) will be opened,while the solenoids 31', 37' and 43' will not be energized so that thevalves 31, 37 and 43 will be closed.

The switches 52 and 53 serve to control the supply of electric currentto the cell 19 to electrolyze any water removed from the sample streamthereby. To this end, the switch 52 has a movable contact arm 70 whichat the beginning of each cycle is normally in engagement with a fixedcontact 71 but is adapted at the proper time to be moved by operation ofthe cam 47 into engagement with a fixed contact 72. The contact 72 isconnected by a conductor 73 to one terminal 74 of the cell 19, the otherterminal 75 of which is connected in series with a current limitingresistor 76 and a conductor 77 to one terminal 7 8 of a conventional lowimpedance electrical current source 79. The other terminal 80 of thecurrent source 79 .is connected by a conductor 81 to the fixed contact82 of the switch 54 which serves to connect a recorder for theelectrolysis current in and out of the cell circuit during part of theoperating cycle as described in detail below.

The switch 54 also has a movable contact 83 which, at the beginning ofeach cycle, engages a fixed contact 82 but is adapted to be moved by thecam 49 at the proper time into engagement with the fixed contact 84. Themovable contact arm 83 of the switch 54 is connected by a conductor 85to the movable contact arm 86 of the switch 53, which, at the beginningof an operating cycle, is normally in engagement with a fixed contact87. The fixed contact 87 is connected by a conductor 88 to the movablecontact arm 70 of the switch 52. The movable contact arm 86 of theswitch 53 is adapted to be moved by operation of the cam 48 at theproper time in the cycle out of engagement with the contact 87 and intoengagement with a fixed contact 89. t

The movable contact arms 83 and 86 of the switches 54 and 53,respectively, are also connected by a conductor 89a to one terminal 90of a switch 91 having a movable con-tact arm 92 connected by a conductor93 to one terminal of a conventional current recording device 95. Theother terminal of the recorder 95 is connected by a conductor 96 to themovable contact arm 97 of a switch 98 which normally engages a fixedcontact 99. The contact 99 is connected by a conductor 100 to themovable contact arm 101 of a switch 102 which normally engages a fixedcontact 103 connected by the con ductor 104 to the conductor 81.

In order to provide a suitable reference reading, say zero, on therecorder 95 corresponding to dry gas, a circuit including an adjustableresistor 105, a fixed resistor 106 and a battery or other source of DC.voltage 107 may be connected between the fixed contact 99 and a secondfixed contact 108 on the switch 98, the contact 108 also being connectedto the conductor 89a. The fixed contact 99 on the switch 98 is alsoconnected by a conductor 109 to a fixed contact 110 on the switch 91,;

so that the connections between. the recorder 95 and the referencevoltage source can be reversed to enable the magnitude of the latter tobe measured, if desired.

The switches 91, 98 and 102 are connected for ganged operation with aswitch 111 having a movable contact arm 112 connected 'by a conductor113 to one terminal of the drive motor circuit for the recorder 95. Theswitch 111 also has a fixed contact 114 connected by a conductor 115 toone side of the power mains, the other side of the power mains beingconnected by a conductor 116 to the other terminal of the recorder drivemotor circuit.

The timer switch 55 serves to turn on the recorder 95 at the proper timein the operating cycle. To this end, it has a movable contact 117 which,at the beginning of each cycle, is in engagement with a fixed contact118 but is adapted to be moved by the cam 50 at the appropriate timeinto engagement with a second fixed contact 119. The movable contact arm117 is connected to the conductor 113 and the fixed contact 119 isconnected to the conductor 115 so that when the two are in engagement,the drive motor for the recorder 95 is connectecl to the power mains.

In connection with the establishment of a reference reading (e.g., zero)on the recorder 95 for the condition when dry gas is passing through thecell 19, as mentioned above, provision should be made for drying thegaseous. sample stream before passing it through the cell 19. Thus, aconventional gas dryer 120 (FIG. 1) may be connected by conduits 121 and122 and valves 123 and 124 on opposite sides of the valve 13 so that byclosing the latter the sample stream may be'dried before it is fed tothe water analysis cell 19.

In a typical operation, let it be assumed that the timer 44 is justbeginning a cycle so that the valves 15 and 22 (FIG. 1) are open, whilethe valves 31, 37 and 43 are closed. Under'these conditions, with thevalve 13 open and the valves 123 and 124 closed, the sample stream,which may be, for example, a gaseous hydrocarbon at a pressure of saylbs. per square inch and containing small amounts of moisture, will flowat a uniform rate through the water analysis cell 19. After'say twentyminutes of the cycle have elapsed, the contact arm 86 of the switch 53is repositioned into engagement with the fixed contact 89 (FIG. 3B).When a further period, say 9.5 minutes has elapsed, the timer 44 (FIG.2) will have driven the cam 46 to the point where it causes the movablecontact arm 56 to disengagethe fixed contact 57 and to engage the fixedcontact 58. This will cause the solenoids and 22' to be deenergized,closing the valves 15 and 22, respectively, (FIG. 1) and the solenoids31, 37' and 43 to be energized, opening the valves 31, 37 and 43. Theseactions are shown graphically on the timing diagrams in FIGS. 3A and 3B.

Under these conditions, the fluid stream no longer flows through thecell 19 but is diverted through the bypass including the open solenoidvalve 31. In its place, dry inert gas which may be, for example,nitrogen is flushed through the cell 19 at a rate of say 10 cubiccentimeters per minute for a predetermined period which may be theremainder of the cycle.

A short time, say a half minute later, the movable contact 70 of theswitch 52 is repositioned into engagement with the fixed contact 72(FIGS. 2 and 3B).

After the cell 19 has been flushed with nitrogen for say, ten minutes,the timer 44 (FIG. 2) will have moved the cam 48 so that the movablecontact arm 86 of the switch 53 is in engagement with the fixed contact87. This in effect connects the conductor 81 to the conductor 73 so thatthe cell is now energized from the source '79 and electrolysis begins.This event is indicated on the timing chart of FIG. 3A. It will benoted, however, that the connection between the movable contact arm 83and the fixed contact 82 of the switch 54 short circuits the recorder 95so that it does not begin to record at this time.

After the electrolysis has proceeded for a predetermined period, say 2.5minutes, the cam 49 causes the movable contact arm 83 of the switch 54to disengage the fixed contact 82 and to engage the contact 84. Thisbreaks the short circuit across the terminals of the recorder 95 so thatit is now connected in series with the cell 19. Shortly thereafter,(e.g., at 43 minutes after the start of the cycle) the timer 44 willhave moved the cam 50 to the position where the movable contact arm 117of the switch 55 is in engagement with the contact 119. This connectsthe conductors 113 and 115 so that power is now supplied to the drivemotor of the recorder 95 and a record strip therein (not shown) beginsto move as a function of time (see FIGS. 3A and 3B).

Several minutes later (e.g., at 45.1 minutes after the beginning of thecycle), the timer 44 causes the cam 49 to move the contact arm 83 intoengagement with the contact 82, again shorting out the recorder 95. Thisis followed (at say 46 minutes) by disengagement of the contact arm 117and the contact 119, so that the recorder drive motor is deenergized.Then, just before the end of the cycle (at say 59 minutessee FIG. 3B)the contact arm 70 of the switch 52 (FIG. 2) is disengaged from thecontact 72, so that the electrolysis current is cut off. The cycle thenrepeats so that a series of records of the electrolysis current atdifferent times are made.

A typical graph, such as might be produced by the recorder 95 is shownin FIG. 4 in which the several discontinuous curves represent therecords made'during successive times when the recorder is on.

If the electrolysis current is plotted against time, integ'fation of thearea under'the curve will give a value proportional to coulombsconsumed. However, it is simplierto take as ameasure of the Watercontent the current at a fixedtime, say five minutes, after electrolysis is initiated (i.e., the point on the-left end of each of the curvesrecorded on the graph in'FIG. 4).

FIG. 5 illustrates a typical calibration curve for the waterdetectingapparatusdescribed above in'wlhich the moisture in -a gaseoussample, in parts per million is plotted as a-function oftheelect-rolysis' current If it is desired to establish a predeterminedreference on therecorder 95 corresponding to" dry gas, the valve 13"(FIG. 1) may be closed and the'valves 1-23 and 124 opened so that the;sample is passed through the gas dryer 120*and" driedbefore beingsupplied to the'cell 19.

With dry gas passing through the cell 19 for one or more cycles ofoperation as described above, the adjustable resistor 105 (FIG. 2) isadjusted to give a predetermined reference reading, say zero, on therecord made by the recorder 95.

The ganged switches 11 1, 102, 98 and 911 which serve to start therecorder drive and to connect the recorder 95 to the bucking voltageappearing at the fixed contacts 99 and 108 of the switch 98 afford meansfor check ing the constancy of the bucking voltage prior to or after anyfluid sample test.

While the flow rate through the water detection system described aboveis not critical, desirably it should be of the order of 100 cubiccentimeters per minute. If it is solwer, less water will be picked upand, it faster, more Water will be picked up.

The timing cycle described above is typical for a flow rate of 100 cubiccentimeters per minute and a pressure of approximately 10 lbs. persquare inch gauge for the sample stream. With higher pressures for thesample stream, the sensitivity of the apparatus will be higher and theoperating cycle may be made shorter.

The system will operate effectively at any temperature between thefreezing and boiling points of water. However, the sample gas pressure,temperature and flow rate should preferably be maintained constant.Moreover, the apparatus may be used effectively for determining thewater content of other gaseous streams such as oxygen streams, forexample.

From the foregoing, it Will be understood that the invention provides ahighly effective method and apparatus for accurately determining thepresence of small quantifies of moisture in fluid streams. By virtue ofthe fact that absorption of moisture from a sample stream andelectrolysis of such absorbed moisture are carried out sequentially,instead of simultaneously as in the prior art, there is no opportunityfor oxygen generated during electrolysis to recombine with any hydrogenin the sample fluid stream passing through the cell to form water whichmight result in spurious readings.

While specific operations and operating cycles, as well as apparatus forcarrying them out, have been described above by way of example, theinvention is not intended to be limited thereto. On the contrary, itencompasses all modifications in form and detail falling Within thescope of the following claims.

We claim:

1. In a method for determining the water content of a specimen gascontaining hydrogen, the steps of passing such gas at a predeterminedrate through a confined space in the presence of a hygroscopic material,then blowing through said confined space a gas substantially dry andnonreactive with hydrogen to remove said specimen gas from said confinedspace while simultaneously bypassing succeeding portions of saidspecimen gas through an alternate route at the same rate of flow, saidwater being retained in said confined space by said hygroscopicmaterial, then decomposing the water retained by said hygroscopicmaterial by electrolysis for a predetermined period of time to indicatea function of said electrolysis.

2. In a method for determining the water content of a specimen gascontaining oxygen, the steps of passing sue-h gas at a predeterminedrate through a confined space in the presence of a hygroscopic material,then blowing through said con-fined space a gas substantially dry andnonreactive with oxygen to remove said speciment gas from said confinedspace while simultaneously bypassing succeeding portions of saidspecimen gas through an alternate route at the same rate of flow, saidwater being retained in said confined space by said hygroscopicmaterial, then decomposing the water retained by said hygroscopicmaterial by electrolysis for a predetermined period of time to indicatea function of said electrolysis.

References Cited by the Examiner UNITED STATES PATENTS OTHER REFERENCESKeidel: Analytical Chemistry, December 1959, vol. 31, No. 12, pp.2043-2048.

JOHN H. MACK, Primary Examiner.

JOSEPH R EBOL D, MURRAY TILLMAN, WINSTON A. DOUGLAS, Examiners.

1. IN A METHOD FOR DETERMINING THE WATER CONTENT OF A SPECIMEN GASCONTAINING HYDROGEN, THE STEPS OF PASSING SUCH GAS AT A PREDETERMINEDRATE THROUGH A CONFINED SPACE IN THE PRESENCE OF A HYGROSCOPIC MATERIAL,THEN BLOWING THROUGH SAID CONFINED SPACE A GAS SUBSTANTIALLY DRY ANDNONREACTIVE WITH HYDROGEN TO REMOVE SAID SPECIMEN GAS FROM SAID CONFINEDSPACE WHILE SIMULTANEOUSLY BYPASSING SUCCEEDING PORTIONS OF SAIDSPECIMEN GAS THROUGH AN ALTERNATE ROUTE AT THE SAME RATE OF FLOW, SAIDWATER BEING RETAINED IN SAID CONFINED SPACE BY SAID HYGROSCOPICMATERIAL, THEN DECOMPOSING THE WATER RETAINED BY SAID HYDROSCOPICMATERIAL BY ELECTROLYSIS FOR A PREDETERMINED PERIOD OF TIME TO INDICATEA FUNCTION OF SAID ELECTROLYSIS.